Elastomeric foam materials, such as polyurethane, are commonly used to form sleeping support pads for humans. Such pads provide a soft surface which deflects proportionally in response to applied loads, dependent upon the density and indentation load deflection (ILD) value of the foam material. ILD values represent an amount of displacement force required to displace a pad a predetermined percentage of a total thickness of the pad. However, a foam pad of homogeneous density and uniform ILD deflects a uniform extent at all areas subjected to a certain minimum load. It has been proposed to layer materials of differing densities and ILDs in order to provide more even support to all parts of a human body in a prone position upon the pad. For example, U.S. Pat. Nos. 3,047,888, 3,833,259 and 3,885,258 each disclose laminated layers of foam materials having differing degrees of resiliency. In these types of laminated foam pads, the top layers are typically of lower density than the lower or inner layers in order to increase the initial softness ratio while maintaining sufficient firmness. This construction limits the types of pads which can be formed to having a soft surface and firm core.
Contoured surfaces have been formed in the top surfaces of top layers of laminate foam pads to improve weight distribution, increase the initial softness ratio, and vary the firmness of the top layer, as described in U.S. Pat. Nos. 4,999,868, 5,022,111 and 5,136,740. U.S. Pat. No. 4,999,868 describes varying the firmness of the top contoured layer by varying the depth of the grooves which form the contours. The grooves are formed entirely within a single top layer of the pad. U.S. Pat. No. 5,022,111 describes formation of contours in outer layers of a pad which have a density greater than an inner layer. However, the contours do not extend into the inner layer. Thus, these approaches do not exploit any of the support characteristic benefits which can be achieved by forming contours or grooves which extend through at least partial cross-sections of multiple laminated layers of differing density.